Commentary for Job 41:5

Who exposed the face of his raiment He returns to the previous topic to speak of the leviathan: who can expose the scales, which are... within his double bridle Into the fold of his lips, when they are open, who is it who will enter there? [The expression] בְּכֶפֶל, double, denotes the lips, which are double, one above and one below, into which no creature may enter because of fear of him.